1. Field of the Invention
The present invention relates to an assembly for transmitting rotational movements and for damping torsional vibrations and which includes a damper housing, a connection section located radially inward of the damper housing for attaching the assembly to a to-be-damped part, with the connection section being formed integrally with the housing as a one-piece part, a cover for sealingly closing the housing and which defines with the housing a working chamber, and a damping weight located in the working chamber in a viscose medium filling the working chamber.
2. Description of the Prior Art
An assembly of a type described above is disclosed in European Patent No. 0 503 424 B1. This patent discloses a torsional vibration damper connected with a belt pulley and designed for use as a crankshaft damper. This assembly, except the damping weight and the damping housing cover, is formed as a single part having a pulley element, damper housing and hub region and which is preferably manufactured by a non-chipping process. This assembly represents a so-called viscose damper which is based on a shear flow of a fluid in an annular clearance between an oscillating weight and a housing provided at a free end of the crankshaft. The freely rotatable oscillating weight, as a result of its rotational inertia, is retarded in its rotation relative to the housing. As a result, the shearing energy of the high viscose fluid absorbs the oscillations of the crankshaft, thus damping the vibrations.
The crankshaft torsional viscose vibration dampers include steel-rubber components the frequency of which is selected to coincide with the first oscillating frequency of the crankshaft to thereby minimize the crankshaft oscillation due to its amortization and damping.
While the use of torsional vibration dampers for crankshaft is conventional, it was not considered to be necessary to use dampers, in addition to those for crankshafts, for a drive train to a camshaft. It is, however, known to use viscose dampers when drives are use for adjusting of the camshaft in order to adapt the ignition points to different rotational regions. The camshafts, which are driven from the crankshafts via toothed belt, chain or gear drives, provide for valve control when internal combustion engines are used. Such a drive train represents a system with distributed masses and has points of different stability, the operation of which is subjected to oscillation due to the intermittent mode of operation of the internal combustion engines. Wide fluctuations of the rotational speeds of the engine are observed due to the intermittent action of the gas forces during combustion in separate cylinders. This is particularly observed at low rotational speeds. This so-called rotational non-uniformity causes a low-frequency rigid body vibration of the entire camshaft which, e.g., in four cylinder, four-stroke engines, results in two gas pulses per revolution. This results in an oscillation angle of the free end of the crankshaft and, thus, of the camshaft drive of .+-.3.degree. and more, especially when the use of a multi-valve technique results in higher gas force pulses or when the mass inertia moment of a flywheel on the crankshaft is reduced by the use of two solid flywheels.
In addition, high frequency torsional vibrations are generated in the camshaft due to the acceleration and deceleration of valve masses. This effect is reinforced in diesel engines because of the drive of the injection pump from the camshaft. The multi-valve technique reinforces these vibrations even more.
Accordingly, an object of the present invention is to provide a damping assembly for a camshaft which would enable a simplified vibration damping of a camshaft, without the use of any adjusting means.
Another object of the present invention is to provide a camshaft vibration damping assembly having the smallest dimensions possible.